In current car manufacturing, the individual design of the vehicles plays an important role. As a result, parts having complex three-dimensional shapes are increasingly required. At the same time, the pressure on costs is high, and therefore efficient and cost-effective production methods are required for complex parts of this type.
One example of parts of this type are clamping strips which are used for receiving combined rubber/plastics elements (2 component elements) for sealing the gap between window panes and side frames of a vehicle body (see FIGS. 4a and 4b). Said strips may have a U-shaped cross section, typically with an opening width of 6 mm or less. Furthermore, said strips may be curved along the length thereof in different planes and may have structures for applying the clamping force and for fastening to the side frame. In order to ensure satisfactory functionality of said strips, the features just mentioned have to be produced with a high degree of accuracy in thin sheets. Difficulties are caused here in particular by the combination of a profile having a relatively narrow opening width with the three-dimensional curvature, and by the introduction of the clamping structures which further reduce the clear width of the profile (for example to 3 mm or less). In addition, elements for fastening the strip to a side frame of a car also have to be introduced into the complex part with sufficient precision.
Clamping strips of the type described above are currently manufactured by a combination of a rolling and bending method 8 and a stretching and bending method 9. In a first rolling and bending method step (see FIGS. 1a and 1b), a starting material 7 is deformed into a profile with a desired cross section by using consecutively arranged pairs of shaping rollers 1a, 1b to 6a, 6b (see FIG. 1b). In this case, the desired target shape is produced successively via a plurality of intermediate shapes by bending from a starting material in the form of a band. In the example illustrated in FIG. 1b, a U-shaped profile is manufactured using six consecutively arranged pairs of shaping rollers 1a, 1b to 6a, 6b. The profile 14 produced in this manner is then provided with the desired three-dimensional curvature in a subsequent stretching and bending step 9. As shown in FIG. 1c, the ends of the profile 14 are clamped for this purpose with the aid of holding devices 13. The workpiece 14 is then bent about a bending mould 12, 16, 17, 18 with the aid of suitable actuators 11, 12. The workpiece 14 can therefore be provided with a desired curvature. Additional features of the clamping strip, such as clamping cams or recesses and perforations for fastening the strip are customarily introduced into the bent profile following the stretching and bending step.